Degree Type

Dissertation

Date of Award

1981

Degree Name

Doctor of Philosophy

Department

Civil, Construction, and Environmental Engineering

Abstract

An extensive review of the literature on design stresses in silos revealed that limiting stress analysis is traditionally used in the design of silos for static lateral stresses, and that overpressures due to the unloading process are allowed for by empirical overpressure factors. It is hypothesized that dilation (volume increase due to shear strain) of the stored material may be a rational explanation for overpressures. Tests in a specially constructed triaxial apparatus indicate that maize, wheat and barley dilate during standard triaxial shear tests, whereas oats, which has higher void ratios, does not. The tests also show that the Mohr failure envelopes are not linear, as normally assumed, but are concave downwards. General expressions for the compression loading tangent modulus and the Mohr failure envelope are developed, and the parameters for the four grains, each at three bulk densities, evaluated. For the maize, wheat and barley, the highest friction angles and initial tangent moduli and the lowest failure strains occur at the intermediate bulk densities. Standard and constant volume tests indicate that stress-strain characteristics are more dependent upon grain packing and stress history, whereas frictional behavior is more dependent upon the geometry and surface roughness of the individual grains.

DOI

https://doi.org/10.31274/rtd-180813-6071

Publisher

Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/

Copyright Owner

David Llewellyn Owen Smith

Language

en

Proquest ID

AAI8209174

File Format

application/pdf

File Size

102 pages

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